Optically active isomers of quinine and quinidine and their respective biological action

ABSTRACT

The present invention provides methods for purifying, identifying and using optically active isomers of quinine and quinidine as well as compositions comprising such optically active isomers. Such optically active isomers having desired actions on cardiac sodium and potassium channel function substantially separable from undesirable effects on GI motility can be useful for more effective therapy of cardiac arrhythmias. Also disclosed are methods for assaying the levels of such isomers present in the biological fluids.

This application claims the benefit of U.S. Provisional Application Ser.No. 60/171,952, filed Dec. 23, 1999, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the resolving ofstereoisomers of quinidine and quinine. More particularly, the inventionrelates to the identification of the biological activity of thedifferent stereoisomers of quinidine and quinine.

2. Description of the Related Art

Quinidine is the most prescribed anti-arrhythmic agent in the UnitedStates. However, the clinical utility of quinidine is limited by theadverse effect of diarrhea In addition, quinidine causes arrhythmias,especially the torsade de pointes variety that results from a long QTinterval. The significant proarrhythmia (worsening of ventriculararrhythmias) associated with quinidine are possibly due to its combinedeffect on both the sodium depolarizing current and the potassiumrepolarizing current.

The first medicinal remedy for the treatment of cardiac arrhythmias isderived from the bark of the cinchona tree, indigenous to South America,where South American Indians long-used cinchona as medication. Europeansbrought the remedy back from their New World explorations. Jean-BaptisteSenac, a French physician, is the first to describe the use of cinchonaextract for cardiac irregularities (Willius, F A, et al., Proc. StaffMeet. Mayo Clin, 1942, 17, 294-296). Subsequently, a ship's captain withthe medical condition auricular (atrial) fibrillation is seen by one ofthe leading European cardiologists, Professor Wenckebach, who had notreatment for the condition (Wenckebach, K F. Die unregelmassigeHerztatigkeit und ihre klinische bedeutung. W. Engelmann, Leipzig,1914). The ship's captain showed Wenckebach how the bark of the cinchonacould control the cardiac irregularity. Following this, Wenckebachpopularized the use of the cinchona extract for arrhythmia therapy. Theprincipal active anti-arrhythmic ingredient of cinchona, quinidine, isidentified in 1918 by the American chemist, Frey (Frey, W. et al., Wien.Klin. Wschr., 1918, 55, 849-853).

While quinidine is still actively prescribed in the United States, itsuse is severely limited by a number of problems. The drug prolongs theQT interval on the electrocardiogram, in a very heterogeneous way,creating a predisposition leading to the development of cardiacarrhythmias, especially Torsade de pointes, which is a rapid ventriculartachycardia. A number of studies have indicated that patients takingquinidine are at a higher risk for death than those not taking quinidine(e.g., Coplen S. E, et al., Efficacy and safety of quinidine therapy formaintenance of sinus rhythm after cardioversion; Circulation 1991;84:527). Quinidine is also limited by severe GI disturbances with themost limiting side-effect being diarrhea. Recent research has shown thatthe drug affects both the cardiac sodium channel and the cardiacpotassium channel, making quinidine a very complex “mixed” action agent(Krafte D. S., et al., Europ J Pharma 1994; 266, 245-254; Snyders D. J.,et al., Molecular Pharma, 1991 41:322-330).

The anti-arrhythmic action of quinidine is thought to be due to itseffect on the sodium channel. Quinidine is classified as a VaughnWilliams type Ia anti-arrhythmic. However, its prolongation of the QTinterval due to APD (action potential duration) prolongation is not wellunderstood. Subsequently, quinidine is found to show a significanteffect in blocking the potassium repolarizing current, thus possessingtype III Vaughn Williams (classification) effect. More recently theprolongation of APD has been found to be both an anti-arrhythmic action,as well as being the basis for the development of a rapid ventriculartachycardia with unique morphology called Torsade de Pointes ventriculartachycardia. Additionally, two potassium channels have been reported tobe critically involved in human repolarization; one being IK_(r) therapid rectifier and the second being IK_(s), a slower ion channel in thehuman myocardium. While the anti-arrhythmic action of many agents onsupraventricular arrhythmia and ventricular arrhythmias are moderatedvia inhibition of sodium channel (ex procainamide) the effect on thepotassium channels (IK_(r) and IK_(s)) may be an importantanti-arrhythmic action. However, strong IK_(r) blocking action oftenleads to pro-arrhythmia of the Torsade de Pointes variety. Thus, achiral isolate that has less IK_(r) action, but retains sodium channelinhibition may offer considerably less pro-arrhythmia. Additionally, anagent causing less contractile augmentation of the GI smooth muscle mayalso be a significant advantage, since so many patients discontinuequinidine due to the diarrhea. Contractile augmentation may not be theonly mechanism of quinidine induced diarrhea. A secretory action ofquinidine may also be an important contributor to the agents diarrhealeffects.

Quinidine has a duplicate drug in nature, quinine, the well knownanti-malarial agent. Quinine is the chemical mirror image of quinidine,similar to the differences of the right from the left hand—identical butcan't overlap, a structural characteristic in chemistry known aschirality. This results in quinidine and quinine being stereoisomers ofeach other. Quinine not only causes constipation, rather than diarrhea,but it affects cardiac ion channels a lot less than quinidine. Thesedifferences come about because of the mirror image relationships of themolecule at one chiral center. Thus, because two different stereoisomersexist that have different configurations, they cannot fit into receptorsthe same way. Since it is assumed that the anti-arrhythmic action, QTprolongation, and diarrhea occur as a result of the molecules acting atspecific receptor sites such as ion channels, it would be anticipatedthat they have differed effects at different ion channels. In fact,stereoisomeric segregation of drug effects is a well establishedpharmacological strategy to determine if a drug acts at a receptor site.Thus, if one stereoisomer is active and the other is not, this is takento mean that the molecule acts at a specific binding site. The fact thatquinidine and quinine are stereoisomers, but have different propertiesimplies that the diarrhea and anti-arrhythmic effects of these drugsoccur through different binding sites and different mechanisms.

However, what is not recognized previously is that there are threeadditional chiral centers on the molecule that then create a total ofsixteen isomers. Besides the optically active site at carbon 2 (C-2)position that segregates quinidine from quinine, there are threeadditional sties at the C-3, C-15 and C-20 carbon positions. Consideringall the possibilities, there are eight possible isomers that havequinidine conformation at the C-2 position. Likewise, quinine also haseight possible isomers, together with quinidine making a total ofsixteen possible stereoisomers.

It is expected that the different stereoisomers of quinidine and quininehave differential biological effects. For example, individualstereoisomers of quinidine or quinine could have different and specificeffects on cardiac potassium channels or cardiac sodium channels. Inaddition, individual stereoisomers of quinidine or quinine could causeincreased GI motility.

The expectation of differential effects of stereoisomers of quinidine orquinine is supported by the many known examples of differentstereoisomers compounds having significantly different biologicalactivity. For example, the different stereoisomers of beta-blockers(e.g. levalbuterol, and beta-amino alcohols), amphetamine (AP),methamphetamine (MAP), and penicillamine have different pharmacologicalactivities and pharmacokinetic behaviors. The S-isomers of AP and MAPare each approximately five times more active on the central nervoussystem (CNS) than their respective R-isomer.

The commercial success of stereoisomers with specific biologicalactivities is demonstrated by the antihistamine terfenadine, thepsychoactive agent fluoxetine and the prokinetic gastrointestinal agentcisapride. Terfenadine is originally sold as a racemate mixture of R-and S-isomers under the name Seldane®. After discovering that racemicterfenadine is preferentially oxidized in rats to form a carboxylic acidmetabolite enriched in the R-enantiomer, Hoechst Marion Roussel beganmarketing the R-isomer of terfenadine as Allegra® (fexofenadine). Asingle isomer preparation of fluoxetine (Prozac) is under developmentand a single isomer version of Zyrtec (cetirizine) may be available inthe near future. A single isomer version of cisapride is marketed asnorcisapride, which has a different receptor binding profile than theparent racemic drug.

Preliminary data regarding the pharmacodynamics of stereoisomers, suchas that mentioned above, suggest that individual isomers can possesssignificant differences in receptor-binding profiles and followdifferent courses of absorption, distribution, metabolism and excretion.As such, the administration of single isomers may significantly reduceif not eliminate drug interactions mediated by the effect ofstereoisomers on different biological receptors. Similar to otherracemic compounds, it is expected that individual stereoisomers ofquinidine and quinine are responsible for the diversity of effectsdisplayed by such compounds (e.g., action on cardiac sodium andpotassium channels as well as effects on GI motility). The ability toidentify isomers of quinidine and quinine with differential effects oncardiac sodium channels, cardiac potassium channels, and GI motilitywould offer considerable potential clinical benefits. For example,specific stereoisomers of quinine or quinidine could be used as drugsfor blocking only cardiac sodium channels or blocking only cardiacpotassium channels while not causing diarrhea. Alternatively, astereoisomers of quinine or quinidine not effecting the cardiac sodiumor potassium channels, but increasing GI motility or mucosal secretioncould be used as novel treatment for constipation or Gastroesophagealreflux disease (GERD). Therefore, the isolation of specificstereoisomers of quinidine and quinine could lead to a safer, less toxicand less pro-arrhythmic compounds than racemic quinidine.

The present invention provides for the isolation of quinidine andquinine stereoisomers. The present invention also provides assays forquantitative determination of optically active isomers of quinine andquinidine in biological fluids. The present invention also provides forassays for measuring the effects of stereoisomers of quinidine andquinine on cardiac potassium and sodium channels, as well ascontractility and secretory assays for determining GI motility activity.

SUMMARY OF THE INVENTION

The present invention provides methods for purifying, identifying andusing optically active isomers of quinine and quinidine as well ascompositions comprising such optically active isomers. Such opticallyactive isomers having desired actions on cardiac sodium and potassiumchannel function substantially separable from undesirable effects on GImotility can be useful for more effective therapy of cardiacarrhythmias. Also disclosed are methods for assaying the levels of suchisomers present in the biological fluids.

In general, the present invention relates to optically active isomers ofquinine and quinidine and to methods of synthesis, isolation,purification, and systems using the same. The invention also relates tothe use of optically active isomers of quinine and quinidine tospecifically block cardiac sodium channels or cardiac potassiumchannels, as well as treating constipation or gastroesophageal refluxdisease (GERD) by increasing gastrointestinal (GI) motility or byincreasing luminal secretion or blocking luminal fluid re-absorption.The present invention also relates to methods of assaying the presenceof optically active isomers of quinine and quinidine in biologicalfluids.

In another embodiment, the invention provides a stereoisomericallypurified form of quinidine. A stereoisomerically purified form ofquinidine is one that contains less than the eight possiblestereoisomers (FIG. 2), in other words, from one to seven. In an evenmore preferred embodiment, this stereoisomerically purified form ofquinidine has a less I_(Kr) effect than commercial quinidine. In anothermore preferred embodiment, the stereoisomerically purified form has lessilleal contractile augmentation than commercial quinidine.

In yet another embodiment, the invention provides a method ofdetermining a therapeutic profile of a compound comprising the steps ofcontacting at least one first recombinantly expressed transmembrane ionchannel with an effective amount of the compound and measuring thechange in the function of the first recombinantly expressedtransmembrane ion channel to determine a first index; contacting atleast one second recombinantly expressed transmembrane ion channel withan effective amount of the compound and measuring the change in thefunction of the second recombinantly expressed transmembrane ion channelto determine a second index; contacting at least one gastrointestinaltissue sample with an effective amount of the compound and measuring thechange in the function of the gastrointestinal tissue sample todetermine a third index; and comparing the relative amplitudes of thefirst, second and third indices to determine the therapeutic profile ofthe compound. The function of an ion channel may be measured by meansknown in the art, such as electrical measurements, includingmeasurements of current, conductance or charge displacement, oralternatively measures of ion flow, including using ion sensors orradioisotopes. In one embodiment, the first recombinantly expressedtransmembrane ion channel is a sodium channel and the secondrecombinantly expressed transmembrane ion channel is a potassiumchannel. Alternatively, any suitable recombinantly expressedtransmembrane ion channel may be used.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example, but not tolimit the invention solely to the specific embodiments described, maybest be understood in conjunction with the accompanying drawings, inwhich:

FIG. 1 shows the structure of quinine and the possible optically activeisomers labeled 1 through 8.

FIG. 2 shows the structure of quinidine and the possible opticallyactive isomers labeled 1 through 8.

FIG. 3 shows the effect of quinidine and quinine on the potassiumchannel (IK_(r)) measured in Xenopus oocytes. Control current isobtained after 4 min. of stimulation pulse from −80 mV to 0 mV at 1200ms (panel A). Quinidine 100 μM significantly inhibits the IK_(r)current. Panel B shows an IV plot of the peak current before and afterquinidine and panel C shows the tail current IV plot. Panels D, E and Fshow the much reduced action of quinine on IK_(r). These results areconsistent with the clinical observation that quinidine prolongs the QTinterval, while quinine usually does not.

FIG. 4 shows a chiral HPLC chromatogram of two peaks, a and b. Theinsert is the mass spectrum which indicates the molecular weight of eachisomer to be 325, corresponding to that of quinidine for each of the twopeaks. Thus, the two peaks are both quinidines, but stereoisomers.

FIG. 5 shows a chiral chromatogram of LC-MS of two peaks, havingretention times of 8.31 and 8.66 min., respectively. The insert is themass spectrum of two peaks. Mass spectrum indicates molecular weight of325, corresponding to that of quinidine for each of the two peaks. Thus,the LC separated the two isomers (or mixture of isomers) of quinidine.

FIG. 6 depicts the effect of the two chirally separated peaks ofquinidine on sodium channel inhibition at various concentrations.

FIG. 7 The effect of the two eluent peaks on the potassium channel(IK_(r)) measured in xenophions oocytes. Peak b shows inhibition similarto a concentration effect relationship as seen with quinidine. Peak ahas a minimal effect.

FIG. 8 shows the effect of amiodarone on IK_(s). Panel A shows that 100μM amiodarone inhibits the current flow across the IK_(s) channel inxenophas oocytes. Panel B shows that at any voltage current (μA) throughthe IK_(s) channel is reduced when 100 μM amiodarone is present.

FIG. 9 represents tracings before and after quinine and quinidine isexposed to a rat illeal strip preparation. Quinidine at 10⁻⁷ and 10⁻⁶M(but not quinine) reduces the magnitude of contraction (trace amplitude)as well as reducing spikes (tall pen deflections). These tracingsconform to the clinical observation that quinidine increase GI motility,while quinine does not.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to the isolation of stereoisomers ofquinine (FIG. 1) and quinidine (FIG. 2). The invention further relatesto the following biological functions of each of the isomers: 1) actionon cardiac potassium and sodium channels and increasing GI motility; 2)action on cardiac potassium channels and increasing GI motility; 3)action on cardiac sodium channels and increasing GI motility; 4) actionon cardiac potassium and sodium channels, without increasing GImotility; and 5) increasing GI motility, without action on cardiacpotassium and sodium channels.

In addition, the present invention relates to methods of isolatingstereoisomers of quinidine and quinine using chiral columns incombination with high pressure liquid chromatography. Chiral columnshave been used to effectively separate stereoisomers (Chan et al., J.Chromatogr. 1991, 571, 291-297). In addition, chiral columns can be usedfor determining enantiomeric purity.

Generally, resolution of stereoisomers of quinidine and quinine can beoptimized through a combination of altering the composition of themobile phase and altering the specific packing materials of the chiralcolumns. Separations are performed using non-polar organic phases (e.g.heptane, iso-octane, etc.) with polar organic additives, such astetrahydrofuran, alcohols, chlorinated hydrocarbons or similar solventswith or without buffer such as phosphate or borate. Often, the additionof a small amount of a strong acid (e.g. trifluoroacetic acid) to themobile phase will considerably improve separation of the isomers. Anionexchange chromatography with aqueous buffers using salt or pH gradientscan also be used to effectively resolve enantiomers of quinidine andquinine.

The present invention also relates to isolating isomers of quinidine andquinine after selective epimerization of protons adjacent to thearomatic ring. Epimerization is usually accomplished by refluxing asolution of the isomers in an acidic medium. However, epimerization isnot limited to this category of chemical reaction. Due to four chiralcenters, quinine and quinidine have a total of sixteen stereoisomers,each of which can possess distinct pharmacological properties. However,some of the stereoisomers of quinidine or quinine may not readily occurdue to the steric hindrance of the rigid bicyclo ring system which doesnot allow conformational flexibility (Karle I. L. et al., Proc. Natl.Acad. Sci. 1981, 78, 5938-5941; Karle J. M., Antimicrob. AgentsChemother. 1997, 41(4), 791-794).

The present invention also relates to assays to determine theelectrophysiological activity of quinidine and quinine compounds byusing voltage clamp techniques. In addition the present inventionrelates to assays to determine the biological activity of quinidine andquinine compounds by performing GI motility studies.

The human heart Na⁺ channel SCN₅A construct encodes the Ina (sodiumchannel) current which is antagonized by class I anti-arrhythmic drugs.Voltage-gated NA⁺ channels are essential for normal electricalexcitability and are responsible for the rapid membrane depolarizationthat characterize the initial phase of the action potential in mostexcitable cells (Catterall W. A., Physiol. Rev. 1992, 72 (4 supp.):S15-48). In myocardium, Na⁺ channel activates rapidly upondepolarization and the fast inactivation contributes to the control ofmembrane refractoriness during repetitive stimulation and is animportant determinant of class I antiarrhythmic drug action (VaughnWilliams E. M. et al., “Class I Anti-arrhythmic Action, chapter 2”; InControl of Cardiac Rhythm, Lippincott-Raven Publishers, New York 1998).Demonstrating dose-dependent antagonism of this channel would thereforeidentify a compound as belonging to the Class Ia antiarrhythmics ofwhich quinidine is the prototypical agent.

The human heart Na⁺ channel clone hHla, which is an expression plasmidof the SCN₅A gene, has been previously described (Kraft D. S. et al.,Molecular Pharma. 1994, 266, 245-254). In brief, the full-length cDNA iscloned into the pGM3 plasmid vector (Promega). The corresponding cRNAcan be injected into Xenopus oocytes whereby the ion channel proteinsare expressed and localized to the cell membrane surface. The ionic fluxthrough the expressed cardiac sodium or potassium channels can then bemeasured. This new technology offers the opportunity to study theeffects of stereoisomers obtained through chiral separation on a definedpopulation of ion channels.

The human ether a-go-go-related gene (HERG) encodes a protein whichassembles to form a transmembrane ion channel. The resulting currentsafter the expression of the HERG gene in Xenopus oocytes indicate thatthe HERG gene encodes a potassium channel with biophysical propertiesidentical to the rapid component of the cardiac delayed rectifier,I_(Kr) (Sanguinetti et al., Cell 1995, 81, 299-307). It is postulatedthat in humans I_(Kr) is a critical component in the repolarizationprocess of the myocardium (Li et al., Circ. Res. 1996, 78, 689-696). TheI_(Kr) current is selectively blocked with high affinity bymethanosulfonalides, such as E-4031, ibutilide, and dofetilide(Sanguinetti et al., J. Gen. Physiol., 1990, 96, 195-215). Thebiophysical properties of the protein encoded by the HERG gene indicatethe gene codes for the cardiac delayed rectifier protein (Trudeau etal., Science 1995, 269, 92-95; Spector et al., J. Gen. Physiol. 1996,107, 611-619; Kiehn et al., Circulation 1996, 94, 2572-2579; Ficker etal., Circ. Res. 1998, 82, 386-395).

The slow component of the cardiac delayed rectifier (I_(Ks)) modulatesthe repolarization of the human cardiac action potential (Li et al.,Circ. Res. 1996, 78, 689-696). The proteins encoded by the KVLQTI andhminK (KCNEI) genes co-assemble to form I_(Ks) (Sanguinetti et al.,Nature 1996, 384, 80-83; Barhanin et al., Nature 1996, 78-80). TheI_(Ks) protein is a target for class III antiarrhythmics (Busch et al.,Eur. J Pharmacol. 1994, 264, 33-37). The K⁺ currents can also be blockedby quinidine, a class I antiarrhythmic agent that also has class IIIaction predominately blocks the rapid K⁺ current I_(Kr). (Synders etal., Mol. Pharmacol. 1991, 41, 322-330).

The SCN₅A gene encodes I_(Na), which are voltage-gated sodium channelsessential for normal electrical excitability. I_(Na) is responsible forthe rapid membrane depolarization that characterize the initial phase ofthe action potential in most excitable cells. In myocardium, thevoltage-gated sodium channels activate rapidly upon depolarization andcontribute to the control of membrane refractoriness during repetitivestimulation. Defects in the fast component of the inactivation ofcardiac sodium channels are responsible for idiopathic ventricularfibrillation syndrome (Chen et al., Nature 1998, 392, 293-296). Ascompared to the fast component, defects in the slow component of theinactivation of sodium channels are responsible for the LQT3 form oflong QT syndrome (Wang et al., Hum. Mol. Genet. 1995, 4, 1603-1607;Bennet et al., Nature 1995, 376, 683-685). Furthermore, the I_(Na)current is a target for class I antiarrhythmics.

Quinidine and quinine have been evaluated in the frog oocyte model.Studies reveal markedly different effects on potassium and sodiumchannels. Studies utilizing 100 μM quinidine reveal marked inhibition ofthe potassium channel while 100 μM quinine had only minimal effects(FIG. 3). Since it is likely that K⁺ channels play a potential role inthe induction of diarrhea, the failure of quinine to affect thesechannels is consistent with its GI effect of causing constipation.Moreover, since quinine has no pro-arrhythmic action thought to beassociated with the K⁺ channel (IK_(r)) effect, the profile observed inthis model with quinine is predictive of the clinical effects of thisdrug.

In yet another embodiment, the stereoisomerically purified compound ofthe present invention can be used as safer anti-arrhythmic and saferanti-malarial agent than either quinine or quinidine.

The disclosures in this application of all articles and references,including patents, are incorporated herein by reference.

The invention is illustrated further by the following examples which arenot to be construed as limiting the invention in scope or spirit to thespecific procedures described in them.

The starting materials and various intermediates may be obtained fromcommercial sources, prepared from commercially available organiccompounds, or prepared using well known synthetic methods.

EXAMPLE 1

Purification of Quinidine. Quinidine is known to contain up to 20%dihydroquinidine as an impurity. In order to obtain pure quinidine(>99%) and avoid interference due to this impurity, commercial quinidine(containing dihydroquinidine) is subjected to purification using HPLC.The HPLC procedure utilizes a C₁₈ μ-Bondapak column operatedisocratically with 0.05 M sodium (or potassium) phosphate buffer (pH3.0) and acetonitrite (73:27, v/v) at a constant flow-rate of 1 ml/min.The UV variable wavelength detector is set at 237 nm and the liquidchromatograph employed is a Spectral Physics Apparatus. Portions of theeluent containing the quinidine (as indicated in the chromatogram) arecollected, concentrated and later subjected to HPLC analysis. Followingseparation, this analysis indicates the quinidine peak to be greaterthan 99.9% pure.

Chromatographic Isolation of Quinine and Quinidine Isomers. Chiralseparation is performed using a Spectra-Physics HPLC instrument and UVvariable wavelength detector set at 254 nm. The chromatographic columnis a pre-packed 25 mm×4.6 mm ID Cyclobond I (5 μm) operated with amethanol—0.014 M sodium perchlorate (75:25 v/v) mobile phase, at a flowrate of 0.2 ml/min. Alternatively, a pre-packed 150 mm×4 mm IDResolvosil BSA-7 column (5 μm) may be operated isocratically with 0.05 Msodium phosphate buffer (pH 3.0)—acetonitrile (73:27 v/v) at a flow rateof 0.2 ml/min.

The identification of each isomer of quinidine and quinine can be madeusing a combination of 2- or 3-dimensional high resolution NMR (¹³C andproton) spectroscopy using a chiral shift reagent, mass spectrometry,and optical activity. In order to obtain isomers of quinidine andquinine having the desired optical purity, eluted samples may need to berechromatographed.

Chiral Separation of Quinidine. Chiral separation is performed using aSpectra-Physics HPLC instrument and UV variable wavelength detector setat 254 nm. The chromatographic column is a pre-packed 250×4.6 mm IDCyclobond I (β-cyclodextrin; 5 μm spherical particles; Alltech Inc.).The mobile phase is CH₃CN (or methanol): NH₄-acetate (0.05 m) buffer(27:73) (v/v), pH adjusted to 3.5 and the instrument is operatedisocratically with a flow rate of 1.0 ml/min. The HPLC analysis resultsin two peaks in the chromatogram with retention times of 5.6 min and 5.9min for peak a and peak b, respectively (FIG. 4). Eluents are collectedat their respective retention times. Mass spectral analysis (usingMicromass-Waters LC-MS #1690 spectrometer) of the aliquots containingboth fractions indicate a molecular weight of 325.4 (FIG. 4), whichconfirms the presence of quinidine isomer(s) in each of the twofractions. The concentration of each fraction is determined from the UVabsorbances compared to those of the known concentrations of quinidinereference samples. The results indicate that each fraction has aconcentration of 1.4 mM/L. Chiral chromatograms of LC-MS of the twoisolated peaks having retention times of 8.31 and 8.66 min. areobtained. Both peaks have a mass spectral analysis indicating amolecular weight of 325 corresponding to quinidine (FIG. 5).

Optical rotations of these isomer fractions are determined using aPerkin-Elmer Polarimeter and the following formula:${{}_{}^{}\lbrack \propto \rbrack_{}^{}} = \frac{100 \propto}{C}$

Where, C=1.4 mMole/L or 0.053 gm/100 ml

-   -   ∝=Polarimeter Reading

Therefore for peak a,$\lbrack \propto \rbrack_{D}^{20} = {\frac{100 \times O}{0.053} = {\pm {O{^\circ}}}}$

For peak b,$\lbrack \propto \rbrack_{D}^{20} = {\frac{100 \times O\quad 0.115}{0.053}\quad = {{+ 217}{^\circ}}}$

The above optical rotation data demonstrates at least partialpurification of the various stereoisomers. However, it is likely thatpeaks a and b do not each contain a single isomer. Thus, these twoisolated fractions may still contain a mixture of isomers probably inuneven proportions.

EXAMPLE 2

Assay for Isomers of Quinine and Quinidine. The following methods areavailable and routinely used for assaying quinine and quinidine inbiological fluids: 1) high-pressure liquid chromatography using normalor reverse phase columns (C₈ or C₁₈) and isocratic or gradient solventsystems and either fluorescence or UV detector (Carignan et al., 1995;Ahokas et al., 1980); 2) solid-phase extraction following by HPLC; 3)enzyme multiplied immunoassay (EMIT); 4) radioimmunoassay followed byHPLC; and 5) fluorescence polarization immunoassay (FPIA) with HPLC.

Examples of Type 1 use a chiral stationary phase (e.g., Resolvosil) inorder to achieve enantiomeric separation of the isomeric compounds ofquinine and quinidine. The liquid chromatograph (Spectra Physics) isequipped with a Resolvosil column protected by a Suplex pkb-100 guardcolumn 20×4.6 mm ID 5 μm particle size and UV variable wavelengthdetector set at 237 nm. The mobile phase consists of a mixture ofaqueous H₂SO₄ solution (0.01 M, pH 2) methanol-acetonitrile (45:45:10)containing 10 mM octanesulfonic acid sodium salt and is filtered througha 0.2 μm Ultipor N₆₆ membrane.

1. Sample Preparation

To a 1.0-ml aliquot of plasma is added 200 μl of the working standardcontaining only the internal standard and 1.0 ml of aqueous K₂HPO₄ (0.2M, adjusted to pH 10 with 5 M KOH). The solution is briefly mixed andthen 5 ml of methyl tert-butyl ether is then added. The tube is cappedand vigorously shaken for 10 min, then centrifuged for 10 min at 2500 g.A 4-ml aliquot of the upper organic phase is transferred to another tubeand evaporated to dryness using a vortex evaporator at 30° C. 2 ml offreshly purified hexane and 200 μl of reconstituting solvent are added,and the tube is vortexed for 2 min. Most of the upper hexane layer isdiscarded. The aqueous phase is washed a second time with 2 ml ofpurified hexane. The aqueous phase is transferred into an autosamplervial, and a 100 μl aliquot is chromatographed.

2. Standard Curve Preparation

Concentrations of quinidine and quinine isomers in samples arecalculated by using a standard curve generated by regression analysis.Standard curve samples are prepared by spiking 1 ml of blank plasma with200 μl of working standard solutions containing isomers of quinine andquinidine and internal standard samples. The standard curve is generatedusing the linear least-squares regression equation to fit the ratios ofpeak height of isomers of quinine and quinidine to the internalstandards against concentrations using a weighting correction factor of1/concentration².

The internal standard is4-diisopropyl-amino-2p-chlorophenyl-2(2-pyridyl)-butyramide or 4-methylpropranolol HCl. The chromatography column and system are the same asabove. The solvent system is used isocratically with 0.05 M sodiumphosphate buffer (pH 3.0)—acetonitrile (73:27 v/v), at a constantflow-rate of 0.2 ml/min. The sample may be prepared using the same asdescribed above.

EXAMPLE 3

Na Channel expression and characterization. The SCN₅A gene encoding thehuman cardiac sodium channel is derived from the hH1A expression plasmid(Gellens et al., Proc. Natl. Acad. Sci. 1992, 89, 554-558; Hartmann etal., Circ. Res. 1994, 75, 114-122). The full-length cDNA is cloned intothe pGEM3 plasmid vector (Promega). The DNA construct is linearized bydigestion with HindIII for runoff transcription. In vitro transcriptionwith T7 RNA polymerase is performed using the Message Machine kit(Ambion). The amount of cRNA synthesized is quantified by theincorporation of trace amounts of [³²P]UTP (phospho uracil threephosphate) in the synthesis mixture. The final cRNA product is thensuspended in 0.1 mM KCI at 200 μg/μl and stored at −80° C. The cRNA isdiluted to a concentration of about 10 pg/nl before oocyte injection.Expression of SCN₅A currents in Xenopus oocytes is obtained after cRNAinjection of the corresponding genes.

For SCN₅A currents the following protocol is used: a) I-V plot, oocytesare kept at a holding potential of −80 mV, then step pulsed from −70 mVto +30 mV in 10 mV increments of 40 ms are applied returning to −80 mV.b) Single pulses, from a holding potential of −80 mV are used. Thencontinuous perfusion of the drug is given over two minutes and the cellis stimulated with a pulse from −80 mV to −10 mV during 25 mins at afrequency of 0.3 Hz. After 4 minutes the peak current is measured at −10mV. Currents are recorded with the conventional two micro-electrodevoltage clamp technique in a bath solution containing in mM: NaCl 96,KCl 2, CaCl 1.8, MgCl 1.0 and HEPES 5, at a pH 7.4. Using thesetechniques the two chirally separated peaks of quinidine demonstratedvery similar properties (FIG. 6).

The results show that both peaks a and b have almost identical doserelated effects on sodium channel inhibition. Thus, both chirallydistinct products have a critical anti-arrhythmic activity, i.e.inhibition of the sodium channel, a fundamental property of VaughanWilliams class I action. It is important to note that sodium channelinhibition does not cause QT prolongation or Torsade de Pointesventricular tachycardia.

EXAMPLE 4

Construction of HERG expression plasmid and cRNA transcription. The HERGgene encoding cardiac potassium channels is similarly derived from thepgH19 construct (Trudeau et al., 1995). For cRNA injection into Xenopusoocytes, the DNA is linearized by NOT1 and in vitro transcription isconducted with T7 RNA polymerase using the Message Machine kit (Ambion).

EXAMPLE 5 Potassium Channel Expression and Characterization

1. I_(Kr)

Wild type human minK (KCNE1) and KVLQT1 cDNA are isolated from humancardiac and pancreas cDNA libraries and cloned into the pSP64 poly (A)vector (Promega). For transcription in oocytes, the minK is subclonedfrom genomic DNA using the MKEL and MKER primers. The final minKexpression construct contains cDNA inserted in the plasmid vector(PROMEGA). For the injection into Xenopus oocytes, cRNA is preparedusing the mCAP RNA capping kit (Stratagene) following linearization ofthe expression construct by restriction digestion with EcoRI for run-offtranscription.

In-vitro transcription is performed with SP6 RNA polymerize using themMessage Machine kit (Ambion). The final capped-cRNA product isresuspended in 0.1 mM KCL and stored at −80° C. The concentration ofsynthesized RNA is estimated by separating the denatured cRNA on a 1.5%agarose gel together with the 0.24-9.5 kb RNA ladder (Gibco-BRL).

HERG currents expressed in Xenopus oocytes are obtained usingconventional two micro-electrode voltage clamp technique in a solutioncontaining in mM: NaCl-96; KCl-5; CaCl-1.8; MgCl-1.0; and HEPES-5, at apH of 7.4. The currents shown have nearly identical biophysicalproperties to the rapid component of the cardiac delayed rectifiercurrent, I_(Kr). From a holding potential of −80 mV, HERG currents areactivated at potentials positive to −50 mV and have a peak current valueat 0 mV. At more positive potentials, the magnitude of the currentprogressively decreases.

Using these methods, recordings are obtained in which peak a of thechiral isolation has a minimal inhibitory effect on the potassiumchannel while peak b has a marked effect in inhibiting I_(Kr).Inhibition of I_(Kr) will lead to an increase in APD duration and thusQT prolongation (peak b).

Since peak a has sodium channel inhibitory activity and no potassiumchannel inhibitory activity, peak a has anti-arrhythmic activity whilenot having the potential pro-arrhythmic action associated with QTprolongation. The preliminary data shows that the two chiral eluentshave two very different properties. One being the typical quinidineeffecting INa and IK_(r) (peak b) while the other is a sodium channelblocker similar to procainamide in cellular anti-arrhythmic action.(peaka) (FIG. 7).

2. I_(Ks) (For Quinidine only, not for Peak a or b)

Wild type human minK (KCNE1) and KVLQT1 cDNA are isolated from humancardiac and pancreas cDNA libraries and cloned into the pSP64 poly (A)vector (Promega). For transcription in oocytes, the minK is subclonedfrom genomic DNA using the MKEL and MKER primers. The final minKexpression construct contains cDNA inserted in the plasmid vector(PROMEGA). For the injection into Xenopus oocytes, cRNA is preparedusing the mCAP RNA capping kit (Stratagene) following linearization ofthe expression construct by restriction digestion with EcoRI for run-offtranscription.

In-vitro transcription is performed with SP6 RNA polymerize using themMessage Machine kit (Ambion). The final capped-cRNA product isresuspended in 0.1 mM KCL and stored at −80° C. The concentration ofsynthesized RNA is estimated by separating the denatured cRNA on a 1.5%agarose gel together with the 0.24-9.5 kb RNA ladder (Gibco-BRL).

KVLQT1+KCNE1 currents are recorded with a solution containing in mmol-L:NaCl-96; KCl-2 CaCl_(2-1.8;) MgCl_(2-1.0;) and HEPES 5, pH 7.4. Thefollowing testing protocols are used: a) I-V plot, oocytes are held at−80 mV, then step pulses from −60 mV to +40 mV in 20 mV increments of 18seconds are applied returning to −40 mV; b) Single pulses, the sameprotocol is applied for control current and after drug perfusion forcurrent measurement. From a holding potential of −80 mV to a testpotential of +40 mV during 18 seconds a pulse is applied. Quinidine isthen infused continuously at a rate of 2 ml/min. over two to fourminutes. The cell is either left at a resting potential of −80 mV orstimulated from a holding potential of −80 mV to a test potential of +40mV during 1000 ms in a frequency range of 0.3 Hz.

The effect of different concentrations of quinidine on the I_(Ks)currents are evaluated at concentrations of quinidine from 10⁻⁶ to 10⁻⁴with a 14 to 52% reduction, respectively (see Table 1 below). Thisinhibition of I_(Ks) is similar to that seen with amiodarone (FIG. 8)and is less than the inhibition seen on I_(Kr) across the concentrationsstudied.

TABLE 1 CONCENTRATION AMIODARONE QUINIDINE (Molar) (% of block) (% ofblock) 10⁻⁶ 15 ± 1 14 ± 5 10⁻⁵ 30 ± 3 21 ± 7 10⁻⁴ 47 ± 1 52 ± 5

EXAMPLE 6

Isolation of oocytes and cRNA injection. Xenopus laevis frogs areanesthetized by immersion in 0.2% Trocaine for 15-30 min. A smallincision is made in the lateral ventral quadrant of the abdomen and asmall piece of ovarian tissue is removed. The incision is then suturedat both the muscle and the cutaneous layers with fine silk thread andthe animal is allowed to recover. The ovarian lobe is digested with 10mg/ml type 1A collagenase (Sigma) in calcium-free solution for 30-60 minto remove the follicle layer. Stage V and VI oocytes are injected with40 nl of a solution containing 10 to 50 ng/μl cRNA of either SCN5A,HERG, or hminK and KVLQT1, and then incubated at 19° C. in a modifiedbath solution for 2-8 days.

EXAMPLE 7

Rat Ileum Studies and Characterization of Chiral Separation Products.Guinea pig ileum is harvested and placed in warm (37° C.) KrebsHanselest buffer and oxygenated (95% O₂ and 5% CO₂). Segmentsapproximately 4.5 cm long are placed on a transducer (GilsonInstruments) and a preload of 1 gm is placed on the tissue. The tissueis then placed in a chamber and bathed in Tyrode's solution (37.5° C.)and oxygenated (95% O₂ and 5% CO₂). Muscle contractions are measuredisometrically. After stable contractions are obtained, a study compoundis added to the tissue bath and recordings are made until a new steadystate of contraction is obtained. Following a washout period, a newsteady state of contraction is recorded and then the procedure repeatedwith a second dose of the drug being evaluated. Changes in contractionmagnitude are recorded as the percentage change from baseline. Thisprocedure is a modification of the technique described by Van Neuten andassociates (Van Neuten et al., Life Sci. 1978 28:453-458). Table 2depicts the effects of quinidine and its derivative chiral products(peaks a and b) on ileum strip contractility.

TABLE 2 Baseline 10⁻⁷ M 10⁻⁶ M 10⁻⁵ M Quinidine Slow waves  2.5 ± 0.5*3.3 ± 0.6 3.0 ± 0.5 6 ± 1 Bursts 8 ± 2 8 ± 2 7.7 ± 1.2 14 ± 4  Spikes 10± 1  11 ± 1  13 ± 2  15 ± 1  Peak a Slow waves 2 ± 0 2.5 ± 1   2.3 ± 0.72.3 ± 0.6 Bursts 4 ± 0 5.7 ± 2   6.2 ± 1   4.8 ± 1   Spikes 11 ± 0  10 ±5  9 ± 3 10 ± 4  Peak b Slow waves 2 ± 0 2.5 ± 0.5 3.2 ± 0.3 4.3 ± 0.6Bursts 4.7 ± 4   7.5 ± 0.9 13 ± 2  20 ± 3  Spikes  10 ± 2.6 19 ± 4  23 ±4  11 ± 3  *mean ± standard deviation

The preparation permits the identification of slow waves of contraction,bursts of contraction of the smooth muscle and spikes of markedcross-sectional contraction. Each of the measures can be used as ameasurement of contractile effect of an agent. Table 2 above shows thatquinidine in a dose response fashion causes an augmentation of slow wavecontractility, burst contractility and spike contractility. Peak a hasminimal effect on slow waves and spikes, and an inconsistent andnon-significant effect on burst frequency. Peak b behaves in ananalogous fashion to quinidine with an increase in all three measures.

A graphic representation of the effect of quinidine and quinine isrepresented in FIG. 9. While quinidine at 10⁻⁷ M and 10⁻⁵ M increasesslow waves (magnitude of pen deflection) and spikes (thin lines shootingup), quinine has no effect.

EXAMPLE 8

Differential Effects of Quinidine and Quinine on I_(Kr).Electrophysiological studies are performed on cardiac potassium channelsusing quinidine (D-isomer) and quinine (L-isomer). I_(Kr) currents areobtained by injection of cRNA from the HERG gene into Xenopus oocytes asdescribed above. Recordings are made with an external [K⁺] of 5 mM, −80mV of holding potential and test potentials of 1200 msec in steps of 10mV from −50 to +40 mV. The peak current is measured at 30 mV. Theeffects of quinidine and of quinine are determined at concentrations of10⁻⁶, 10⁻⁵, and 10⁻⁴ M.

The IC₅₀ for I_(Kr) block is 6.4±1.9 μM for quinidine and 80.2±2.1 μMfor quinine. At 0.33 Hz stimulation frequency, the percent block forquinidine is 33±6 (10⁻⁶ M), 42±2 (10⁻⁵ M), and 83±2 (10⁻⁴ M), while thepercent block for quinine is 10±3 (10⁻⁶ M), 21±6 (10⁻⁵ M), and 52±10(10⁻⁴ M). Quinidine (D-isomer) blocks I_(Kr) 12.5 times greater thanquinine (L-isomer). The current block for the two isomers is dosedependent with quinidine being an order of magnitude more potent thanquinine. The difference in quinidine and quinine on cardiacelectrophysiology may be clinically useful and may explain the higherincidence of proarrhythmia with torsade de pointes (toxic arrhythmia)seen with quinidine therapy as contrasted to quinine therapy.

Conclusions

The data shows that further chiral separation of quinidine initiallygives two chromatographic peaks. The two peaks have distinctly differentproperties as to the inhibiting action on the potassium channel (IK_(r))as well as on GI contractility (illeal step preparation). One eluent(peak b) has properties similar to quinidine in that it inhibits thepotassium channel IK_(r) in an analogous fashion to quinidine, while asecond peak does not inhibit the IK_(r) current (peak a). Both eluentseffect the sodium channel similarly. The eluent that does not effectIK_(r) does not increase illeal contractility. These results segregatetwo toxic effects of quinidine to one isomer (or a mixture of isomers),while leaving another free of potential cardiac and GI toxicity.

The invention and manner and process of making and using it, are nowdescribed in such full, clear, concise and exact terms as to enable anyperson skilled in the art to which it pertains, to make and use thesame. It is to be understood that the foregoing describes preferredembodiments of the present invention and that modifications may be madetherein without departing from the spirit or scope of the presentinvention as set forth in the claims. To particularly point out anddistinctly claim the subject matter regarded as invention, the followingclaims conclude this specification.

1. A stereoisomerically purified form of a compound selected from thegroup consisting of quinine and quinidine, wherein thestereoisomerically purified form has different effects on cardiac ionchannels and on gastric motility compared to the stereoisomericallyunpurified form of the compound, wherein the stereoisomerically purifiedform of a compound is selected from the group consisting of:(1R)((2R,4R,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2R,4R,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2R,4S,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2R,4S,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2S,4R,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2S,4R,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2S,4S,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2S,4S,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2R,4R,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2R,4R,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2R,4S,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2R,4S,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2S,4R,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2S,4R,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2S,4S,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2S,4S,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;and mixtures thereof.
 2. The stereoisomerically purified form of claim 1wherein the compound is quinidine.
 3. The stereoisomerically purifiedform of quinidine of claim 2 having from one to seven stereoisomers ofquinidine.
 4. The stereoisomerically purified form of quinidine of claim3 having less effect on I_(Kr) than a stereoisomerically unpurified formof quinidine.
 5. The stereoisomerically purified form of quinidine ofclaim 4 having less QT prolongation than a stereoisomerically unpurifiedform of quinidine.
 6. The stereoisomerically purified form of quinidineof claim 5 having less Torsade de Pointes ventricular tachycardia effectthan a stereoisomerically unpurified form of quinidine.
 7. A compositionsuitable for the treatment of arrhythmia comprising thestereoisomerically purified form of quinidine of claim 3 and apharmaceutically suitable excipient.
 8. The stereoisomerically purifiedform of quinidine of claim 3 having a sodium channel effect similar tothat of a stereoisomerically unpurified form of quinidine, having lesseffect on I_(Kr) than that of a stereoisomerically unpurified form ofquinidine, and having less gastrointestinal side-effects than astereoisomerically unpurified form of quinidine.
 9. A method forstereoisomerically purifying a compound, the compound selected fromquinine and quinidine, the method comprising passing the compoundthrough a chiral column and obtaining a stereoisomerically purified formof the compound, wherein the stereoisomerically purified form of thecompound is selected from the group consisting of(1R)((2R,4R,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2R,4R,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2R,4S,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2R,4S,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2S,4R,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2S,4R,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2S,4S,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1R)((2S,4S,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2R,4R,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2R,4R,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2R,4S,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2R,4S,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2S,4R,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2S,4R,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2S,4S,8R)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;(1S)((2S,4S,8S)-8-vinylquinuclidin-2-yl)(6-methoxy(4-quinolyl))methan-1-ol;and mixtures thereof.
 10. The method of claim 9 wherein the compound isquinidine.
 11. The method of claim 10 wherein the stereoisomericallypurified form of quinidine has from one to seven stereoisomers ofquinidine.
 12. A method for treating cardiac arrhythmias in a patienthaving a need for such treatment comprising administering to the patientan effective amount of the stereoisomerically purified form of acompound of claim
 1. 13. The method of claim 12 wherein the cardiacarrhythmia is selected from the group consisting of an atrialarrhythmia; a ventricular arrhythmia; or an atrial arrhythmia and aventricular arrhythmia.
 14. A method for treating malaria in a patienthaving a need for such treatment comprising administering to the patientan effective amount of the stereoisomerically purified form of acompound of claim
 1. 15. The stereoisomerically purified form of acompound of claim 1 wherein the compound is quinine.
 16. Thestereoisomerically purified form of quinine of claim 15 having from oneto seven stereoisomers of quinine.
 17. The stereoisomerically purifiedform of quinine of claim 16 having less effect on I_(Kr) than astereoisomerically unpurified form of quinine and having less reductionof gastric motility than a stereoisomerically unpurified form ofquinine.
 18. A composition suitable for the treatment of malariacomprising the stereoisomerically purified form of quinidine of claim 17and a pharmaceutically suitable excipient.
 19. A stereoisomericallypurified compound, or mixture of said compounds, according to claim 1,wherein the compound or compounds have less or no QT prolonging action,and wherein the compound or mixture compounds possess prokinetic GIeffects, compared to the unpurified form of the compounds or mixture ofcompounds.
 20. A stereoisomerically purified compound, or mixture ofsaid compounds, according to claim 1, wherein the compound or compoundshave the same, less or no QT prolonging action, wherein the compound ormixture compounds possess anti-arrhythmic action due to sodium channelblocking, and wherein the compound or mixture of compounds do notpossess prokinetic GI action or a lesser degree of GI stimulation,compared to the unpurified form of the compounds or mixture ofcompounds.